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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        /* ...arr  可以将一个数组展开 */
        var arr = [1,2,3]
        console.log(arr);
        console.log(...arr);
        var a=[4,5,6]
        var b = [7,8,9]
        a.push(...b)
        console.log(a);
    </script>
</body>
</html>